1. Field of the Invention
The present invention relates to the handling of hot glass sheets. More particularly, the present invention relates to a lifting mold especially useful for lifting glass sheets into vacuum engagement with the downward facing surface of a vacuum mold of curved configuration in a vacuum forming operation of the type depicted in U.S. Pat. No. 3,846,104 to Samuel L. Seymour wherein the glass sheets to be shaped are of irregular or non-rectangular outline or shaped to non-uniform elevational contours and weigh as much as or more than 50 pounds (23 kilograms).
The bending and lifting molds incorporated in such apparatus are of the outline type and often have a rigid rail of T-shaped section and ring-like outline. The rail may either be unitary or sectionalized and is shaped to conform to the outline of the glass sheet undergoing shaping to serve as a shaping mold. A heat-softened glass sheet is conveyed into a position above the ring-like mold when the latter is in a vertically recessed or lowered position. The ring-like mold then lifts the glass sheet when the latter is properly aligned vertically. The vertical movement of the outline ring-like shaping mold brings the hot glass sheet into close adjacency to an upper vacuum mold having a downward facing surface conforming throughout its extent to the shape desired for the glass sheet and approximating the outline shape provided by the ring-like mold.
Because of the extreme weight of the glass, it is necessary to make the ring-like mold of very heavy metal to develop the desired rigidity for the outline mold. It has been customary in the past to insulate the heavy material from direct contact with the glass. Such insulation reduces the effect of the high heat capacity of the ring-like mold to impart tension stress in the engaged glass sheet, which tension stress weakens the glass.